New Species Publication

We are proud to announce a new paper coming out in the International Journal of Systematic and Evolutionary Microbiology, “Geobacter daltonii sp. nov., an iron(III)- and uranium(VI)-reducing bacterium isolated from the shallow subsurface exposed to mixed heavy metal and hydrocarbon contamination,” by Om Prakash, Tom Gihring, Dava Dalton, Kuki Chin, Stefan Green, Denise Akob, Greg Wanger, and Joel Kostka. This paper describes a new species of Geobacter isolated from the contaminated subsurface of a nuclear legacy waste site in Oak Ridge, Tennessee, managed by the U.S. Dept. of Energy.


Dr. Om Prakash, the lead author on this paper, cultivated a full 3 grams of G. daltonii to show that the genotype of the new strain is very different from its closest relative, G. uraniireducens (DNA-DNA hybridization value of 21 %). Here is Om with a giant flask of the uranium-breathing bug.


In this paper, we isolated an iron(III)- and uranium(VI)-reducing bacterium from highly contaminated sediments of the Oak Ridge Integrated Field-Scale Subsurface Research Challenge (OR-IFRC) sponsored by the U.S. DOE Environmental Remediation Sciences Program (ERSP) and led by the Oak Ridge National Laboratory, in Oak Ridge, Tennessee. The sediments here are exposed to nuclear legacy waste contamination including radionuclides and hydrocarbons. Our analysis of the 16S rRNA gene and the Geobacteraceae-specific citrate synthase (gltA) mRNA gene sequences from ORFRC sediments indicate that this G. daltonii is both abundant and active in subsurface sediments undergoing uranium(VI) bioremediation.

Cells of G. daltonii are Gram-negative, non-spore forming, curved-rods and form pink colonies in a semisolid cultivation medium, a characteristic feature of the genus Geobacter, and is an obligate anaerobe. Similar to other members of the Geobacter group, G. daltonii conserves energy for growth from the respiration of Fe(III)-oxyhydroxide coupled to the oxidation of acetate. It is also highly versatile metabolically and, unlike its closest relative G. uraniireducens, can utilize formate, butyrate, and butanol as electron donors and soluble ferric iron (as ferric citrate) and elemental sulfur as electron acceptors. Based on the phylogenetic analysis and phenotypic differences we observed, in this paper we determine that this new strain is in fact a whole new species in the Geobacter genus and we name it Geobacter daltonii. The strain was named to honor Joel Kostka’s former laboratory technician Dava Dalton, an author on this paper who performed the initial isolation of the strain and tragically passed away shortly thereafter.

This paper has been a long time coming and many authors put a lot of effort into this project. Congratulations to everyone on this new and exciting publication!